Korean Patent Laid-Open Publication No. 10-2008-0054531 discloses a traveling apparatus for a wheel loader. The traveling apparatus includes an acceleration pedal that is provided with a first hall sensor and a second hall sensor, which are disposed at a lower portion thereof and generate a signal for forwardly or backwardly moving the wheel loader, a loader controller that receives the signal generated from the first hall sensor and the second hall sensor of the acceleration pedal and generates a signal to fit each situation in consideration of the current speed and state of the loader, an engine fuel injection controller that receives the signal from the loader controller and controls a fuel injection amount to control the speed, and a forward and backward traveling controller that receives the signal from the loader controller and selects the forward or backward traveling of the loader in response to a value of the received signal. In addition, the loader controller can control the vehicle speed of the loader depending on the speed and time thereof upon the sudden change of the traveling direction.
The Korean Patent Laid-Open Publication No. 10-2008-0054531 discloses that only the acceleration pedal is used to select the forward or backward traveling of the loader to perform a traveling operation, but does not disclose a precise control that is present between the acceleration pedal and the actual traveling operation.
A conventional construction, for example, a wheel loader includes various work modes. All the work modes include a traveling operation. In particular, an acceleration pedal stepping amount determines the speed of the loader during the traveling operation of the loader. For example, a loading work and a carrying work of a dump truck requires a detailed acceleration operation according to a low speed traveling thereof. However, there is a disadvantage in that the detailed operation performed during the low speed traveling thereof depends upon only a skilled operator's feeling. Accordingly, in the case where a detailed traveling operation is repeatedly performed, the operator requires a very high attention, and thus he or she easily feels a fatigue, thereby causing a safety accident. In addition, the conventional construction loader entails a shortcoming in that a traditional mechanical brake used upon the deceleration thereof consumes the kinetic energy of the loader as heat of a brake disc, thereby resulting in a deterioration of energy consumption efficiency.
A conventional construction machine employing an engine encounters the above-mentioned problem, but recently, a hybrid system starts to be applied to a mechanical field, and the development of improvement of fuel efficiency is in progress. The hybrid system is configured to control the electric motor used in the drive of the hybrid system through the electric generator so that kinetic energy of the machine is converted into electric energy which is in turn stored in an energy storage system (ESS). The electric energy stored in the energy storage system (ESS) is re-used for a subsequent work or traveling operation. As such, the hybrid system can improve the fuel efficiency. However, since the drive characteristics of the electric motor are different from that of the engine, sophistication can be reduced during the detailed work. In addition, the conventional hybrid system has a problem in that since it generates regenerative energy using a braking force that is previously set and fixed in the braking operation, there is a limitation in the amount of the regenerative energy generated through the deceleration of the construction machine.